Using the idea that no one (or no website) can be all things to all people you could think about focusing on 'elements' to optimize and rank well for instead of verbiage/content.
Add video and images, podcasts and downloads (etc) then optimize for those elements. The second most used search vehicle on google is images.
Also, since you mentioned using directories, each of these elements has a slew of directories, for example there's podcastdirectory.com and podcast.net, RSS feeds have their own directories, downloads, video... just about everything does.
Also, portals dedicated to a topic advertise somewhere, I'd thoroughly research where your competitors advertise and run an ad campaign pointing to your site and highlighting an option/favor/benefit you have and they don't. Once they're there you need a way to capture their info so you can write back and ask for the link.